Derivatives (Gain Or Loss Of Reclassified Accumulated Other Comprehensive Income And Recognized In Income) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income	$ 15,670	[1]	$ (4,951)	[1]	$ 23,846	[1]	$ (4,619)	[1]
Amount of Gain or (Loss) Recognized in Income	1,387	[2]	3,731	[2]	(606)	[2]	1,822	[2]
Oil And Natural Gas Revenue [Member] | Commodity Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income	15,670	[1]	(3,520)	[1]	23,846	[1]	(2,885)	[1]
Amount of Gain or (Loss) Recognized in Income	1,387	[2]	3,731	[2]	(606)	[2]	1,822	[2]
Interest Rate Swaps [Member] | Interest, Net [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income	0	[1]	(1,431)	[1]	0	[1]	(1,734)	[1]
Amount of Gain or (Loss) Recognized in Income	$ 0	[2]	$ 0	[2]	$ 0	[2]	$ 0	[2]

[1] Effective portion of gain (loss).

[2] Ineffective portion of gain (loss).